Connecting piece assembly and process container

Disclosed is a connecting piece assembly for a process connection of, in particular, fittings or sensors. The connection piece assembly having a first stationary connecting piece element and a second replaceable connecting piece element which is designed so as to be at least partly receivable by a receiving opening of the first stationary connecting piece element. The second replaceable connecting piece element has an outer thread for attaching a union nut of the fitting or the sensor. The connection piece assembly further includes at least one holding device which is designed to hold together the first stationary connecting piece element and the second replaceable connecting piece element. Also disclosed is a process container with a corresponding connecting piece assembly.